1. Field of the Invention
The present invention relates to a composition for the production of a polyimide film for a flexible board of a photoelectronic device. More specifically, the present invention relates to a composition for the production of a polyimide film that has good dimensional stability without causing a rise in the stress of a substrate despite high-temperature heat treatment.
2. Description of the Related Art
In recent years, lightweight and compact devices have gained importance in display applications. Currently available glass substrates are heavy, tend to be brittle, and are difficult to apply to continuous processes. Under these circumstances, considerable research efforts have been made to replace glass substrates with lightweight flexible plastic substrates that are applicable to continuous processes and to apply such plastic substrates to mobile devices, such as cell phones, notebooks, and PDAs.
Particularly, polyimide (PI) resins are easy to synthesize, can be formed into thin films, and are not required to have cross-linking groups for curing. Due to these advantages, polyimide resins have been actively investigated for use in semiconductor materials, such as LCDs, PDPs, OLEDs, solar cells, and electronic papers, and lightweight flexible plastic display boards with the recent increasing demand for lightweight and high-precision electronic devices.
Polyimide (PI) films refer to films produced using polyimide resins. Polyimide resins are highly heat resistant resins that are typically produced by solution polymerization of an aromatic dianhydride and an aromatic diamine or diisocyanate to prepare a polyamic acid derivative, followed by dehydration ring closure at a high temperature to imidize the polyamic acid derivative.
Boards for flexible displays are produced by coating a polyimide resin solution on a glass substrate and heat treating the coated substrate at a high temperature to form a film. At this time, a difference in coefficient of thermal expansion (CTE) between the underlying glass substrate and the polyimide film layer causes warpage of the glass substrate after formation of the film. This warpage makes it difficult to laminate a device on the film, rendering subsequent processes impossible to carry out.
There is thus a need to develop a composition for the production of a polyimide film that can prevent an underlying substrate from being warped by a difference in CTE from the substrate.